Successive mycological nail tests for onychomycosis: a strategy to improve diagnosis efficiency

Abstract

Onychomycosis is a fungal infection of nails caused by dermatophytes, yeasts and moulds, accounting for about 50% of onychopathies. A high frequency of onychomycosis caused by Candida species has been reported during the last few years in northeast Brazil, as well as in other regions of the world. A clinical diagnosis of onychomycosis needs to be confirmed through laboratory exams. We evaluated the importance of serial repetition of direct microscopic exams and fungal culture for the diagnosis of onychomycosis in the city of Fortaleza, Ceará, in northeast Brazil. We first made a retrospective study of 127 patients with onychomycosis, identifying the fungi that had been isolated from fingernails and toenails. We then made a prospective study of 120 patients, who were submitted to three successive mycological examinations. Ungual residues were scraped off and directly examined with a microscope and fungal cultures were made. In the retrospective study, in which only one sample was analyzed, the incidence of onychomycosis was 25.0%. In our prospective study, in which we had data from successive mycological examinations, 37.8% had onychomycosis. The most commonly isolated fungi in both studies were yeasts from the genera Candida, especially C albicans, C. parapsilosis and C. tropicalis. We found a high proportion of onychomycosis caused by Candida species. We also concluded that serial repetition of direct microscopic examination and fungal culture, with intervals of 2-5 days improved the diagnosis of onychomycosis. We suggest that this laboratorial strategy is necessary for accurate diagnosis of this type of mycosis, especially when the standard procedures fail to diagnose fungal infection, despite strong clinical suspicion.

Onychomycosis: clinical, mycological and in vitro susceptibility testing of isolates of Trichophyton rubrum

“…was the main causative agent. 18,26 Considering that these microorganisms may be contaminant or colonize bodily areas with no clinical implication, they can only be considered the etiology of onychomycosis when their culture isolation is associated with the presence of tortuous hyaline hyphae in DME, which occurred in our study, or when the same NDFF is isolated from repeated samples collected at two or more different times and there is no growth of dermatophytes. 2,26,27 …”

“…18 In this context, Meireles et al 18 propose performing mycological tests in three consecutive samples collected at intervals from 2 to 5 days, which is proven to increase diagnostic accuracy.…”

Comparison of In Vitro Antifungal Activities of Efinaconazole and Currently Available Antifungal Agents against a Variety of Pathogenic Fungi Associated with Onychomycosis

“…There were no significant increases in MICs in T. rubrum and T. mentagrophytes (4)(5)(6). Several studies have confirmed the role of these organisms as causative pathogens, although their relative incidence compared to Trichophyton infections is low (14)(15)(16). Further, mixed fungal infections occur in approximately one-fifth of onychomycosis cases and may be a reason for clinical treatment failure (17,18).…”

Epidemiology, Causative Agents and Clinical Features of Onychomycosis in El-Gharbia Governorate

“…Fingernail onychomycosis is more commonly associated with yeast infection, particularly Candida spp. (Meireles et al, 2008). The main nondermatophyte molds involved in onychomycosis are Scopulariopsis, Aspergillus, Fusarium, Penicillium and Scytalidium species (Narain & Bajaj, 2016).…”